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| /petsc/src/ksp/pc/impls/fieldsplit/ |
| H A D | fieldsplit.c | diff 21635b76ed28834bc274bfdfd6051f93dfbfcb4f Sun Mar 31 19:22:47 UTC 2013 Jed Brown <jed@59A2.org> PCFieldSplit: make Schur complement use normal iterative solver by default
Consider the block system
J = [A B; C D]
where S = D - C A_inner^{-1} B. It is common that if an iterative solve
is performed with S, that A_inner^{-1} uses the same solver
configuration as A^{-1}. PCFieldSplit required this until
514bf10dab8e522ec43f5ccc117d5d97e4aaca18, when the option of a distinct
A_inner was added. In that commit, the default inner solver for A^{-1}
was (likely unintentionally) changed to KSPPREONLY, as a side-effect of
calling MatSchurComplementSetKSP() with no modifications.
This patch reinstates the original default, in which A^{-} =
A_inner^{-1} is defined by GMRES instead of PREONLY. Note that it is
also common to use PREONLY for S, in which case S may not be used
directly, and the user is responsible for setting an inexact method for
fieldsplit's A^{-1}.
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